ARM: OMAP2+: Fix ti81xx devtype

Otherwise we get error "Cannot detect omap type!" and many
things can fail with following:

Unhandled fault: imprecise external abort (0xc06) at 0xc6031fb0

This is because the omap_type is being used to set up th SoC
specific functions for omaps.

Cc: Brian Hutchinson <b.hutchman@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>